PROJECT SUMMARY Population trends in aging present public health challenges in countries such as the USA and UK. Consequently, age-related health conditions such as sarcopenia (loss of muscle mass) are becoming increasingly prevalent. Oral health problems also increase dramatically with age, particularly tooth loss, periodontal disease, dry mouth, denture-related problems and chewing difficulties. Poor oral health has been implicated as a risk factor for sarcopenia. However, the extent to which and what particular oral health markers contribute to an increased risk of sarcopenia is not well-established. Moreover, the pathways or mechanisms by which oral health might influence sarcopenia are poorly understood. Current research is mostly from studies that are cross-sectional or have limited measures of sarcopenia and oral health in older populations. Such studies are not able to establish the contribution of oral health markers to the development of sarcopenia. To address these scientific evidence gaps, we aim to utilise data from two unique well-characterised cohort studies in the UK and USA. Our overarching goal is to investigate the contribution of oral health to the development of sarcopenia, and to understand the mechanisms underlying this relationship. Our research objectives are to: 1) determine the extent to which markers of poor oral health (periodontal disease, tooth loss, dry mouth, denture problems, chewing difficulties) are associated with incidence of sarcopenia over a 6-year follow-up; 2) determine the role of dietary factors as potential mechanisms underlying the association of poor oral health with incidence of sarcopenia; and 3) determine the role of inflammation as mediators of the association of poor oral health with incidence of sarcopenia. These will be achieved through secondary data analyses of two large population-based longitudinal studies of older people in the UK and USA, which are uniquely-placed for these investigations. These studies have detailed data on oral health, dietary factors, inflammation, as well as sarcopenia over time. The British Regional Heart Study is the only such longitudinal study of older people in the UK. The study comprises participants from 24 towns across Britain, followed-up at age 71-92 years in 2012 and at 77- 98 years. The US Health, Aging and Body Composition Study offers complementary data in a population-based study of older people from Memphis and Pittsburgh followed-up from age 71-80 years. These investigations based, on novel conceptual hypotheses and cross-country comparisons in UK and US studies, will significantly advance our understanding of the role that oral health plays in an important geriatric condition such as sarcopenia. The goal of this research is to provide the scientific basis for better identification and management of oral health conditions in older people, and to identify targets for interventions to reduce sarcopenia. These efforts are ultimately aimed at better health of older people.